Document Type

Honors Project

Publication Date



Lake Michigan dwelling dune thistle, Circium pitcheri, is a federally threatened plant, whose reproduction is affected by a non-native weevil, Larinus planus. Originally introduced as a biological control agent to combat the spread of Canada thistle, Circium arvense, this weevil is instead using C. pitcheri as a host for its larvae. Associational susceptibility is an important factor to consider in hopes of preventing the damage to this endangered plant. The goal of this study was to observe L. planus behavior to determine why there is a correlation between increased density of beach grass and high levels of C. pitcheri damage. We hypothesize that C. pitcheri’s neighboring grass community is used as a dispersal aid for the non-native weevil, making neighboring thistle hosts more susceptible to weevil damage in grassy environments. To test this, we conducted ethogram studies at Whitefish Dunes State Park (WDSP) in Door County, WI. At WDSP, we found that L. planus physically used beach grass to get to C. pitcheri and largely failed to disperse using the sand. These results should help provide ecologically sustainable management strategies, while also promote more in-depth host specific analyses prior to the release of biological control agents.

Level of Honors

cum laude




Alyssa Hakes